Proton beam cancer therapy is fast becoming a mainstream technology in the US, offering the potential for successful cancer treatment with minimum damage to adjacent healthy tissue. The main advantage of proton beam therapy is its ability to target small tissue volumes within a patient, with very high precision, potentially down to fractions of a millimeter. Precisions far greater than can be achieved with x-ray radiotherapy. The reduced damage to healthy tissue translates directly to fewer side effects and shorter patient recovery times. Achieving the maximum benefit of proton beam therapy requires an image-guided approach, since the targeting accuracy of proton beam therapy is easily compromised by patient motion, either as a result of insufficient immobilization or the inevitable motion due to patient respiration or cardiovascular action. Present practice for proton beam cancer therapy does not use an image-guided approach. Typically, digital x-ray radiography is done prior to proton beam irradiation, (usually from two orthogonal views), to construct a 3-D x-ray image of the tumor for targeting. This x-ray imaging must be done off-line, with the proton beam switched off, since proton irradiation creates a significant neutron flux, which rapidly destroys silicon-based x-ray detector panels. The actual proton beam treatment is typically delayed, until the x-ray detectors are retracted behind shielding. In this SBIR effort, Structured Materials Industries, Inc., (SMI) www.structuredmaterials.com, will develop an x-ray imaging system, which is highly resistant to damage by particle beam radiation such as protons and neutrons. The proposed x-ray detector system can be used directly prior to, or even in-situ during proton beam cancer therapy, enabling cancer treatment options that take maximum advantage of the benefits of proton beams. Our technical approach will use thin films of man-made diamond, as the active semiconductor material in the x-ray detector, instead of present technology silicon. Diamond has a number of advantages for use in radiation detectors, including high-sensitivity, low-noise and excellent radiation hardness, as will be detailed further in this proposal. Recent developments in technology to produce synthetic diamond are now making this material available and affordable for electronic applications. PUBLIC HEALTH RELEVANCE: The proposed x-ray imaging system will enable high precision dose delivery, during proton beam cancer therapy. This increased accuracy will enable destruction of cancerous tissue, with minimal damage to adjacent healthy tissue, even with the inevitable organ movement due to patient respiration and cardiovascular action. Greater beam position accuracy will enable treatment of advanced tumors, small tumors and tumors intimately adjacent to healthy organs, as well as lead to shorten recovery times.